1. Field of the Invention
This invention relates in general to print output apparatus and methods, and more particularly, to a method and apparatus for electromagnetic drying of printed media.
2. Description of Related Art
In electronic print devices for printing, copying and desktop publishing systems, images are usually offered in electronic form, and are then referred to as electronic images. These electronic images can be stored on magnetic disk or transported via direct links or networks to the print devices. The creation of a page results in an electronic data stream or electronic file describing the several elements of the page layout in electronic format. This electronic page layout is usually expressed in a page description language. The electronic page layout comprises the data for each electronic image that must appear on the printed reproduction.
Several print technologies exist today to provide the printed reproduction of each electronic image including, but not limited to, inkjet and laser technology. For inkjet printing, the printer sprays tiny droplets of ink onto the print media, to recreate the electronic images onto hard copy. Many of the inks used in inkjet technology are water based, so the ink's solvent must be able to evaporate or be absorbed into the media, e.g., continuous web, within a reasonable amount of drying time. Drying of the ink is the process of absorption or evaporation of the ink's solvent into the web or atmosphere while the pigment ideally remains on the surface. Drying techniques can be employed to facilitate the drying of the ink, so that for example, the ink's pigment remains at the web surface with minimal ink spread and feathering to produce sharp, dense images. Power dissipated in the inked web helps to facilitate drying at a faster rate.
High-speed, inkjet printers must be able to dry the ink of the printed media very quickly and with reasonable power constraints. One method of drying the printed media uses a heated drying unit.
In addition to the excessive power consumption problem of the heated drying unit, a safety and scorching hazard is introduced when the paper is delayed while passing through or across the heated drying unit. Since the drying unit is slow to cool, the safety and scorching hazard may remain active for some time. Furthermore, the operator must wait a lengthy time for the dryer to cool to avoid a burn hazard when clearing paper from the dryer.
An additional problem encountered with dryers is that the elements used by the dryers are slow to heat. This time directly adds to the warm-up time required by the printer. Obviously, any warm-up time required by the printer adds to the total time required by the print job, which ultimately slows the operation of the printer.
A further problem posed by radiant heat dryers is the selectivity to the color of the ink. For example, darker colored ink may get hotter than the lighter colored ink and thus evaporate at a faster rate than does lighter colored ink. Multicolored media, such as preprinted forms, when exposed to the radiant heat, may experience local puckering of the media where the ink is darkest. Conversely, lighter colors may not dry as well, since less heat may be absorbed by the lighter colored ink, which causes slower evaporation of the water content.
It can be seen, therefore, that there is a need for a method, apparatus and article of manufacture for providing instant-off, instant-on drying for printed media. Not only does the efficiency of the drying increase, but so does the safety of the device. Furthermore, a more uniform method of drying is required so that inked media may be dried at approximately the same rate, regardless of the color of the ink used.